group1=c(2)
group2=c(1)
formula="z~karnof+race+gender+symptom+str2+cd4.0+wtkg"
ACTG175_wide=reshape(ACTG175,idvar = c("pidnum"), timevar = "time", direction = "wide", v.names=c("cd4"))
ACTG175_wide=ACTG175_wide%>%filter(arms%in%c(group1,group2))
ACTG175_wide$z=(ACTG175_wide$arms==2)+0